diff options
Diffstat (limited to 'Documentation/usb')
| -rw-r--r-- | Documentation/usb/URB.txt | 21 | ||||
| -rw-r--r-- | Documentation/usb/proc_usb_info.txt | 9 |
2 files changed, 16 insertions, 14 deletions
diff --git a/Documentation/usb/URB.txt b/Documentation/usb/URB.txt index 00d2c644068..50da0d45544 100644 --- a/Documentation/usb/URB.txt +++ b/Documentation/usb/URB.txt @@ -195,13 +195,12 @@ by the completion handler. The handler is of the following type: - typedef void (*usb_complete_t)(struct urb *, struct pt_regs *) + typedef void (*usb_complete_t)(struct urb *) -I.e., it gets the URB that caused the completion call, plus the -register values at the time of the corresponding interrupt (if any). -In the completion handler, you should have a look at urb->status to -detect any USB errors. Since the context parameter is included in the URB, -you can pass information to the completion handler. +I.e., it gets the URB that caused the completion call. In the completion +handler, you should have a look at urb->status to detect any USB errors. +Since the context parameter is included in the URB, you can pass +information to the completion handler. Note that even when an error (or unlink) is reported, data may have been transferred. That's because USB transfers are packetized; it might take @@ -210,12 +209,12 @@ have transferred successfully before the completion was called. NOTE: ***** WARNING ***** -NEVER SLEEP IN A COMPLETION HANDLER. These are normally called -during hardware interrupt processing. If you can, defer substantial -work to a tasklet (bottom half) to keep system latencies low. You'll -probably need to use spinlocks to protect data structures you manipulate -in completion handlers. +NEVER SLEEP IN A COMPLETION HANDLER. These are often called in atomic +context. +In the current kernel, completion handlers run with local interrupts +disabled, but in the future this will be changed, so don't assume that +local IRQs are always disabled inside completion handlers. 1.8. How to do isochronous (ISO) transfers? diff --git a/Documentation/usb/proc_usb_info.txt b/Documentation/usb/proc_usb_info.txt index c9c3f0f5ad7..98be9198267 100644 --- a/Documentation/usb/proc_usb_info.txt +++ b/Documentation/usb/proc_usb_info.txt @@ -54,9 +54,12 @@ it and 002/048 sometime later. These files can be read as binary data. The binary data consists of first the device descriptor, then the descriptors for each -configuration of the device. Multi-byte fields in the device and -configuration descriptors, but not other descriptors, are converted -to host endianness by the kernel. This information is also shown +configuration of the device. Multi-byte fields in the device descriptor +are converted to host endianness by the kernel. The configuration +descriptors are in bus endian format! The configuration descriptor +are wTotalLength bytes apart. If a device returns less configuration +descriptor data than indicated by wTotalLength there will be a hole in +the file for the missing bytes. This information is also shown in text form by the /proc/bus/usb/devices file, described later. These files may also be used to write user-level drivers for the USB |